Studies conducted by regulatory bodies in various countries have revealed that most of the radio frequency spectrum is inefficiently utilized. Allocation of fixed spectrum (assigned to specific services) prevents rarely used frequencies from being used by unlicensed users, even when there is no threat of interference at all with any of the assigned services
Advances in the wireless technology along with the development of analog and digital electronics have led to the emergence of wide range of wireless and radio access technologies. There is a huge demand for the availability of spectrum with the increased number of applications in the wireless communications space. With the existing radio frequency spectrum, being pushed to its boundaries there is a limitation on the spectrum availability.
To address spectrum scarcity issue and to satisfy the increased demand of applications new methods are needed for efficient and intelligent use of spectrum.
Wireless communication systems like cognitive radios are working towards allowing the wide frequency spectrum to be shared thus enabling efficient radio spectrum utilization. Cognitive radio devices use dynamic spectrum management system and can identify available/idle frequencies/frequency bands the spectrum that can be used for communications. Multiple cognitive radio systems generally share information to find vacant spectrum bands.
For cognitive radios to succeed, it is essential that they must be software defined, capable of operating on a broader frequency range, have better interference management, strong spectrum sensing and also have re-configurability in terms of operating parameters like frequency, input/output power, receiver sensitivity, bandwidth and so on based on the radio environment. Broad frequency range of operation (for spectrum sensing, interference management and communication) and reconfigurabilty of operating parameters depends on the design of the RF front end.